perf: skip es-module-lexer if have no dynamic imports (#12732)

packages/vite/src/node/plugins/dynamicImportVars.ts

@@ -7,6 +7,7 @@ import { dynamicImportToGlob } from '@rollup/plugin-dynamic-import-vars'
 import type { KnownAsTypeMap } from 'types/importGlob'
 import type { Plugin } from '../plugin'
 import type { ResolvedConfig } from '../config'
+import { CLIENT_ENTRY } from '../constants'
 import {
   createFilter,
   normalizePath,
@@ -20,6 +21,11 @@ import { toAbsoluteGlob } from './importMetaGlob'
 export const dynamicImportHelperId = '\0vite/dynamic-import-helper'
 
 const relativePathRE = /^\.{1,2}\//
+// fast path to check if source contains a dynamic import. we check for a
+// trailing slash too as a dynamic import statement can have comments between
+// the `import` and the `(`.
+const hasDynamicImportRE = /\bimport\s*[(/]/
+
 interface DynamicImportRequest {
   as?: keyof KnownAsTypeMap
 }
@@ -162,7 +168,11 @@ export function dynamicImportVarsPlugin(config: ResolvedConfig): Plugin {
     },
 
     async transform(source, importer) {
-      if (!filter(importer)) {
+      if (
+        !filter(importer) ||
+        importer === CLIENT_ENTRY ||
+        !hasDynamicImportRE.test(source)
+      ) {
         return
       }